SHAd-256 Test Vectors

SHAd-256 (also written as SHA_d-256,
SHA_d256, SHAd256, etc.) is an iterative hash function introduced
by Niels Ferguson and Bruce Schneier in their book, Practical
Cryptography. Like NMAC and HMAC, SHAd-256 is designed to
avoid length extensions that are possible with
ordinary SHA-256 (and most other iterative hash functions). This page
provides test vectors for SHAd-256, which are missing from the
book.

SHAd-256 is defined as follows:

SHAd-256(m) := SHA-256(SHA-256(m))

As of this writing, SHAd-256 has not received much peer review,
so using it instead of HMAC-SHA-256 is not recommended. The main purpose of
posting these test vectors is to aid implementation of Fortuna (also
introduced in Practical Cryptography), which uses
SHAd-256.